The present application is base on Japanese priority application No. 2002-201384 filed Jul. 10, 2002, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to semiconductor devices and, more particularly, to a semiconductor device having a built-in contact-type sensor such as a fingerprint sensor and a manufacturing method of such a semiconductor device.
While electronic information communication spreads, the demand for individual identification has increased in electric equipment so as to observe the confidentiality of personal information. Although various technologies as means for personal identification have been developed and put into practical use, the technology for distinguishing a fingerprint has attracted attention. A semiconductor device in which a contact-type sensor using electric capacitance is incorporated as a small device for distinguishing a fingerprint has been developed.
2. Description of the Related Art
Generally, a fingerprint sensor referred to as a capacitance-type recognizes a fingerprint based on a change in the capacitance that is generated by bringing a finger tip into direct contact with a sensor surface. The fingerprint sensor called a sweep-type reads a fingerprint image by a sensor surface being swept by a finger. For example, a fingerprint image can be recognized by sensor surface being swept by a finger even if the sensor surface has a width as small as 1 mm. For this reason, the sweep-type fingerprint sensor is a mainline among fingerprint sensors that can be incorporated into portable equipment.
The electric-capacitance sensor used as a fingerprint sensor can be formed on a silicon substrate like a semiconductor element. That is, a fingerprint sensor can be produced as a part of a semiconductor chip that is formed of a silicon substrate.
FIG. 1 is a cross-sectional view of a semiconductor device having a built-in sweep-type fingerprint sensor in a state in which the semiconductor device is incorporated in a housing of an electronic device. In FIG. 1, bumps 1c of the semiconductor device 1 having a built-in fingerprint sensor is connected to a flexible board 2 through an anisotropically conductive resin 4.
The semiconductor chip 1 is incorporated in a housing 3 of an electric device in a state in which a fingerprint sensor area 1b is exposed on a circuit formation surface 1a. That is, the fingerprint sensor area 1b is exposed to outside since it is necessary to move a finger while the finger is brought into contact with the fingerprint sensor area 1b. 
Since the fingerprint sensor area 1b is generally formed in the circuit formation surface 1a of the semiconductor chip 1, the fingerprint sensor area 1b is provided on the same surface as a surface on which the bumps 1c, which serve as terminals for mounting the semiconductor chip 1 to the flexible board 2, are provided. In the case of the example shown in FIG. 1, the bumps 1c that are protrudingly formed on the circuit formation surface 1a of the semiconductor chip 1 are connected and fixed to electrode pads 4a formed in the pattern wiring 4 of the flexible board 2 by an anisotropically conductive resin 5.
In the structure shown in FIG. 1, the fingerprint sensor area 1b of the semiconductor chip 1 is a part, which is directly contacted by a finger, and must be exposed outside of the housing 3 of the electric device to be incorporated.
As mentioned above, since the fingerprint sensor area 1b is a part, which is directly contacted by a finger, there may be a case in which a finger cannot be completely brought into contact with the fingerprint sensor area if the peripheral portion of the exposed part is high. Particularly in the case of a fingerprint sensor device of the sweep-type, the width (X direction of FIG. 1) of the fingerprint sensor area 1b is as small as about 1 mm, a finger may not contact sufficiently if the peripheral portion is high. Therefore, the end of the flexible board 2 is not covered by the housing 3, thereby being exposed to outside of the housing 3.
When the end of the flexible board 2 is exposed, an external force may be exerted on the end of the flexible board 2. For example, when moving a finger in an opposite direction (a direction opposite to the direction X), a force may be exerted on the end of the flexible board 2 which may cause the end of the flexible board to move upward. The end of the flexible board 2 is the connection portion to which the semiconductor chip 1 is connected, and, thus, if an upward force is exerted on the end of the flexible board 2, the end of the flexible board 2 may be separated from the semiconductor chip 1 if the bonding force of the anisotropically conductive resin 5 is small. In this case, the electric connection between the semiconductor chip 1 and the flexible board 2 is deteriorated, which may cause a problem that the fingerprint sensor does not function well.
It is a general object of the present invention to provide an improved and useful semiconductor device having a built-in contact-type sensor in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device having a built-in contact-type sensor in which a connection portion between a semiconductor element and a wiring board is protected.
In order to achieve the above-mentioned invention, there is provided according to one aspect of the present invention a semiconductor device having a built-in contact-type sensor, comprising: a semiconductor element including a built-in contact-type sensor having a sensor area formed on a circuit formation surface and connection terminals provided in an area other than the sensor area; a wiring board connected to the connection terminals of the semiconductor element so that an end surface of the wiring board is positioned on the circuit formation surface; and a protective resin part covering a part extending from the end surface of the wiring board to the circuit formation surface.
According to the present invention, the end of the wiring board is covered by the protective resin part, and is firmly fixed to the circuit formation surface of the semiconductor element. Thereby, the end of the wiring board is prevented from separating from the semiconductor element due to an external force, which prevents failure of the semiconductor device due to separation of the wiring board from the semiconductor element.
Additionally, there is provided according to another aspect of the present invention a semiconductor device having a built-in contact-type sensor, comprising: a semiconductor element including a built-in contact-type sensor having a sensor area formed on a circuit formation surface and connection terminals provided in an area other than the sensor area; a wiring board connected to the connection terminals of the semiconductor element so that an end surface of the wiring board is positioned on the circuit formation surface; and a resin filled between the wiring board and the semiconductor element and covering the end surface of the wiring board.
According to the above-mentioned invention, the end of the wiring board is covered by the resin filled between the wiring board and the semiconductor element, and is firmly fixed to the circuit formation surface of the semiconductor element. Thereby, the end of the wiring board is prevented from separating from the semiconductor element due to an external force, which prevents failure of the semiconductor device due to separation of the wiring board from the semiconductor element.
Additionally, there is provided according to another aspect of the present invention a semiconductor device having a built-in contact-type sensor, comprising: a semiconductor element including a built-in contact-type sensor having a sensor area formed on a circuit formation surface and connection terminals provided in an area other than the sensor area; and a wiring board connected to the connection terminals of the semiconductor element so that an end surface of the wiring board is positioned on the circuit formation surface, wherein the end surface of the wiring board positioned on the circuit formation surface forms an inclined surface with respect to the circuit formation surface.
According to the above-mentioned invention, the end surface of the wiring board located on the circuit formation surface of the semiconductor element inclines, and, thus, a force exerted on the inclined end surface does not act in a direction which separate the end of the wiring board from the circuit formation surface of the semiconductor element.
In the semiconductor device according to the above-mentioned invention, a conductive part may be formed in the vicinity of the oblique surface on a surface opposite to a surface of the wiring board facing the semiconductor element, and the conductive part may be electrically connected to grounding wires included in wires formed on the wiring board.
Additionally, there is provided according to one aspect of the present invention a semiconductor device having a built-in contact-type sensor, comprising: a semiconductor element including a built-in contact-type sensor having a sensor area formed on a circuit formation surface and connection terminals provided in an area other than the sensor area; and a wiring board having wires on a surface facing the semiconductor element and connected to the connection terminals of the semiconductor element so that an end surface of the wiring board is positioned on the circuit formation surface, wherein a conductive part is formed in the vicinity of the end surface of the wiring board on a surface opposite to the surface of the wiring board facing the semiconductor element, and the conductive part is electrically connected to grounding wires included in the wires formed on the wiring board.
According to the present invention, since the conductive part formed on the front surface of the end of the wiring board is connected to the grounding wire, a static charge accumulated on the fingertip flows to the grounding wire by the fingertip contacting the conductive part prior to contacting the sensor area of the semiconductor element. Thereby, the sensor area can be protected from a static charge.
Additionally, there is provided according to another aspect of the present invention a manufacturing method of the above-mentioned semiconductor device, comprising the steps of: removing a part of a base material sheet of the wiring board and forming the wiring board in the base material sheet in a state where a part of the wiring board is connected to the base material sheet; locating the semiconductor element over an end surface of the wiring board formed in the base material sheet and a part of the base material sheet other than the wiring board; connecting connection electrodes of the semiconductor element to electrodes formed on the end surface of the wiring board; and cutting a part of the wiring board connected to the base material sheet so as to separate the wiring board from the base material sheet.
Since the semiconductor element is supported by the end of the wiring board and the base material sheet until the wiring board is separated from the base material sheet, easy handling of the base material sheet can be achieved during the manufacturing process.
In the manufacturing method according to the present invention, the step of locating the semiconductor element may include a step of placing the base material sheet on a bonding stage having a first surface and a second surface, a step corresponding to a height of the connection electrodes of the semiconductor element formed between the first surface and the second surface so that the end surface of the wiring board is placed on the first surface and a part of the wiring board other than the end surface of the wiring board is placed on the second surface.
Accordingly, even when the electrode is formed only on one side of the semiconductor element, the semiconductor element can be maintained horizontally on the bonding stage when mounting the semiconductor element. Thus, bonding can be performed easily.
Other objects, features and advantages of the present invention will become more apparent from the scope of the present invention.